Variable pitch boat propeller



July 30, 1963 H. H. sxMsHAUsl-:R 3,099,320

VARIABLE FITCH BOAT PROPELLER me@ Aug. 1, 1960 s sheets-sheet i Wil ATTORNEYS July 30, 1963 H. H. slMsHAUsER VARIABLE FITCH BOAT PROPELLER Filed Aug. l, 1960 5 Sheets-Sheet 2 INVENTOR HfRE/ar /v S/MSHA Us5/e mman/#m ATTORNEYS July 30, 1963 H. H. slMsHAusER 3,099,320

VARIABLE FITCH BOAT PROPELLER Filed Aug. 1, 1960 5 Sheets-Sheet :5

INV EN TOR Hem ER r 5ms/M0551? Mmm/51H04@ ATTORNEYS 3,099,320 VARIABLE PI'ICH BAT PROIELLER Herbert H. Simslxauser, Box 342, RJ). 2, Ravenna, Ohio Filed Aug. 1, 1960, Ser. No. 46,655 "i Claims. (Cl. 17d-160.13)

This invention relates .to variable pitch boat propellers and more particularly, to a two-speed variable pitch outboard motor propeller in Iwhich the propeller blades automatically shift vfrom a low pitch position at slow boat speeds to a high pitch position at higher speeds including an integral means -for selectively reversing the pitch of the propeller blades.

The use of outboard motors is becoming increasingly popular and there is great demand for .a versatile motor capable of high cruising speeds and very slow speeds tor trolling and maneuverin-g through crowded anchorages and around dock areas. Because practically all outboard motors are Z-cycle, it has not been possible to provide a powerful engine that will run at high speeds and yet throttle `down .to very low speeds `for long p-eriods as is required :for trolling. 'Ihis is due to the .fact that the oil in the gasoline necessary r,for lubrication of the motor quickly fouls the spark plu-gs at low speeds.

In attempts to solve Ithe above problem, various devices have been used to slow the boat `speed while running the motor at a sufficiently high number of rpm. to prevent fouling of the spark plugs, the most common of these `devices being trolling plates clamped on the back of the propeller to reduce its eiciency considerably. These plates are inconvenient 4to .attach and -detach as the occasion `demands and .are often lost or dropped overboard during installation.

Recently, some outboard motors have been provided with two-speed transmissions. While vsuch devices are effective to allow the motor Vto run at a high enough number of r.p.m. to prevent fouling of the spark plugs rwithout propelling the boat at a proportionate speed normally obtained at such rpm., these transmissions substantially increase the weigh-t and cost of the motor.

ln yfurther `consideration of the transmission problem, the -weight and cost are further increased by the need for a reverse gearing arrangement to change the direction of rotation of the propeller shaft to `drive the boat in a reverse direction.

A further disadvantage of prior art type devices is that the variable pitch action of the propeller blades is effected by .the difference in water pressure on either side of the blades acting about an off-center longitudinal axis about which the blade is rotatably or pivotally mounted.

ln view of the foregoing considerations, it is an 0bject of this invention to provide an automatic variable pitch propeller wherein the `full thrust of the propeller is used to vary the pitch as opposed .to the diierential pressure created on the blades.

Another object of this invention is to provide an automatic variable pitch propeller including an integral blade pitch reversing mechanism whch precludes the need for -a reverse gearing transmission.

Still another object of .this invention is to provide an automatic variable pitch propeller including an integral blade pitch reversing mechanism wherein the blade pitch varying means and the reversing means are `combined in the same blade shifting mechanism with the operation of the reversing means being selective as opposed Kto the ful-ly automatic operation of the pitch varying means.

Still another object of this invention is to provide an automatic variable pitch boat propeller 'in which the propeller blades are in a low pitch position for slow boat speeds and automatically shift .to a high pitch position 3,099,32@` Patented July 30, 1963 2 'for higher speeds, the pitch position being a function of the amount of propeller thrust as determined by the number of rpm. at which the propeller is rotated.

Still vanot-her object of this invention is to provide an automatic variable pitch boat propeller assembly in which the propeller blades shift automatically from a position of low pitch to high pitch when the number of r.p.rn. of the assembly is above or below, respectively, a predetermined limit, the shifting to high pit-ch position being effected by the increase in propeller thrust and the return to ylow pitch position being effected by spring means having a biasing force acting in opposition to and greater than the propeller thrust at a number ot rpm. below said predetermined limit.

A further object of this invention is to provide a variable pitch propeller with integral pitch reversing means which may be made in any suitable size and number of propeller blades and used with any engine lfor which a propeller of such a size is adopted.

These and other objects of this invention will become apparent with reference .to the following specitication and drawings fwhich relate to several preferred embodiments of the invention.

Aln the drawings:

FIG. l is an end view of one embodiment of .the invention;

FIG. 2 is a side elevation of the embodiment shown in FIG. 11;

FIG. 3 is a cro-ss-section taken along line 3-3 of FIG. `l;

IFIG. 4 is a detailed cross-section taken along line 4-4 of FIG. il;

FIG. 5 is a detailed showing of one of .the elements of .the invention;

FIG. 6 is a detailed showing of another element of the invention;

FIG. 7 is an oblique cross-section of another embodiment of the invention;

FIG. 8 is .a side elevation of the gear box and shifting means of an outboard motor as adapted to this invention;

FIGS. 9 `and 9'(a) are top and oblique views, respectively of a detail of the invention.

Referring in detail to the drawings, and more particularly to FIGS. 1 .and 2, the propeller 10 is shown as comprising a hub 12 having `a cylindrical section 12 with plurality of propeller blades 14 mounted therein such that the pitch of the blades may be varied.

Each blade 14 has a mounting assembly 16 comprising an integral shaft 18 extending substantially axially from the blade 14 into a mounting block 20 which is pivotally mounted within a substantially rectangular housing slot 22 in the cylindrical hub section 12. As shown in FIGS. 1 :and 7, both of the slots 22 are oifset and parallel with respect to a common diameter of the end-face of crosssection of the cylindrical hub section 12. Each slot has an open end at the periphery ofthe cylindrical hub section 12 for removably receiving the mounting blocks 20 and a closed end 24 Within Ithe hub section for a purpose to be later described herein.

Referring to FIGS. 4, 5 and 6 and further with respect to FIGS. 1 and 2, the detailed structure of the blade mounting means 16 is shown.

In FIG. 5 the blade shaft 18 is shown as being rotatably mounted in a cylindrical passage 26 within the lower long dimension of the mounting block 20. An annular boss or collar 28 on the shaft 18 serves as .a thrust bearing or limit stop which abuts the outer end face 30 of the mounting block 2i). The shaft 18 and the collar 28 thereon are snugged-up in the cylindrical passage 26 by means of a concentric take-up screw 32 'threaded in the end of the shaft 18 .and having an enlarged head 34 in contact with the inner end face 36 of the mounting block 2d.

Immediately adjacent the outer end of the annular boss or collar 2S on the blade `shaft 18 is a bifurcated open ended blade actuating lever 36 extending radially outward from the peripheral surface thereof. rihis structure is shown in enlarged detail in FIG. 6. The bifureated actuating lever 36 cooperates with a fixed pin 3S, extending from the periphery of the hub section 12 immediately adjacent the open end of the housing slot '22 which slidably 'engages the lever 36 between the bifurcations thereof. Thus, the blade shaft 18 is caused to pivot about its longitudinal axis and change the pitch of the blade 14 in a' direction depending on the relative movement of the shaft V1S with respect to the fixed pin 38.

Relative movement between the blade shafts 18 and the fixed pins 38 is provided by the pivoted mounting of the blade mounting blocks 2@ lin the slots 22.

Referring to FIGS. 4 and 5 in conjunction with FIG. 2, the mounting blocks 2GZ are shown as having a dependent hinge ear 40 having a bore 42 therein for receiving a pivot pin 44. The head 46 of the pivot pin 44 is shown `in FIG. 2 in its mounting block retaining position wherein the head 46 is in a peripheralrecess 48 in the propeller hub 12. Each of the pivot pins 44 extend through the innermost part of the recesses 22 parallel to the closed end wall 24. The pins 44 are spaced from the end walls 24 a sufficient distance to allow pivotal movement of the mounting blocks of an extent calculated to change the pitch of the blades 14 from an extreme forward pitch to an extreme reverse pitch.

The blade mounting blocks '20 4are normally biased to- Wardthe extreme position which results in a reverse pitch of the blades 14 when they aire indexed, by a means to be later described, to a reverse sense by compression springs 50 embedded in recesses 52, shown Iin dotted lines in FIGS. l .and 5, and abutting the inner end walls 24 of the mounting slots 22 inthe hub 12.

As will be hereinafter described, the blade mounting block 20 may be indexed to a position wherein the propeller blades 14 assume a forward pitch, in which case the springs 24 bias the entire blade mounting assembly 16 toward the position corresponding to minimum forward blade pitch.

The indexing means for the forward `and reverse conditions of blade pitch is shown in FIGS. 3, 4, 5, 9 and 9(a) in detail and more generally in FIGS. l and 2.

Basically, the indexing means comprises a shift rod 54 slidably mounted in a xed concentric sleeve 56 extending axially out of the end face of .the hub section 12. A locking nut 57 retains the sleeve in the hub i2 by forcing an upper shoulder 57' into abutting relation with -the upper end face of the hub section 12.

The fixed sleeve 56 has a cavity 518 therein which is internally disposed with respect to the hub section 12. A blade pitch indexing cam means `6ft is mounted on the inner end of the shift rod 54 and housed in the cavity 58 of the fixed sleeve 56 for reciprocation therein. The cam means 60 is shown in detail in FIGS. 9 and 9(a) as a generally rectangular bar having alternate opposite cam faces 62 on either side of cen-ter of the shift rod S4. An indexing or locking surface 63 is disposed below each cam surface 62 on the cam bar 6d for a purpose to be hereinafter described. The cam surfaces 62 extend radially one from either side of the fixed sleeve 56 through a second or centrally disposed guide slot 64 in the hub section 12. This guide slot 64 is also shown in the solid hub embodiment of FIG. 7.

The guide slot 64 on the hub section 12 is shown in FIGS. 1, 4, and 7 as being perpendicular to both of the mounting block housing slots 22 and hence, the cam bar 166 disposed therein extends perpendicularly into the slots 22.

Referring now to FIGS. l, 4 and 5, and particularly to FIG. 5, the blademounting block 20 shown as having a cam bar receiving slot 66 cut in the face thereof adjacent the inner walls of the mounting bloc-k housing slots 22. A cooperating cam face 68 for each of the cam faces 62 on the cam bar dii is provided on an inner surface of each cam bar receiving slot 66. Thus, when the cam bar 16d is reciprocated in the guide slot 64 by means of the shift rod 54, the cam surfaces 62 thereon engage the internal cooperating cam surfaces 68 in the blade mounting blocks 2i? and a sliding camming action is created.

thereby which pivots the mounting block Ztl about the fixed pins Also, adjacent each cam surface 63 in the slots 66 is a cooperating indexing or locking sunface 69 which cooperates with the .indexing surface 63` on the cam bar 6i? to latch the shi-ft rod 54- in its extended position against the action of the spring 5d.

The actual adaptation of the variable pitch propeller of this invention to an outboard motor is shown schematically in FIG. S. In this showing, the solid hub embodiment of FIG. 7 is shown in cross-section. It is seen that for this particular embodiment the shift rod 54 and the attached cam bar 6d do not ride in a fixed sleeve within the hub 12 itself. The shift rod 54 is concentrically journalled within the propeller drive shaft 7 0 which extends from the engine transmission, indicated by bevel gears 7,2 and 74, to the propeller hub 12. The cam bar `60 and the o-uter end of the shift rod 54 are merely housed in the guide slot 64 for reciprocation therein.

They engine output shaft 76 is connected through bevel `gears 74 and 72 to the propeller drive shaft 70. Since the rotation is unidirectional and it is desired to change the direction of propeller thrust without the shifting of gears, means is provided for reciprocating the shift rod 54 to vary the pitch of the propeller blades from forward to reverse and vice-versa.

. ing clamp or the like 82.

The pitch shifting means on the engine comprises a Bowden cable or the like 73 attached to one arm of a ivoted L-shaped shift lever 80' by means of a connect- The other arm of the shift ever dit is connected by means of a stirrup 84 on the tip thereof to a yoke 86 on the innermost end o-f the shift rod 54.

Thus, the shift rod is reciprocated when the Bowden wire 4is yenergized to oscillate the shift lever I8d about its pivot 8S.

The portion of the outboard motor housing 9G 'which is shown is that portion which is submerged when the motor is in actual use.

Operation The complete interrelation of the various elements having been defined above, the operation of the manually controlled pitch reversing means and the thrust operated automatic forward pitch varying means will now be described.

When it is desired that a forward dri-ving thrust be exerted by the propeller 10, see FIG. 8, the Bowden wire 78 is actuated Ito depress the adjacent arm of the shift lever 89 via the clamp means 82. This rocks the shift lever Sti about its pivot point 88 and causes the stirrup 84 thereon to pull the shift rod 54 and the attached cam bar 60 inward with respect to the motor housing 90 (FIG. 8), or upward as shown in FIGS. l, 2, 3 and 4, by means of the yoke 86 on the inner end of the shift rod 54.

As the shift rod 54 and the attached cam bar 6G` rnove inward or upward as defined above, the cam surfaces 62 on the cam bar 60y engage the inner cooperating cam surfaces 68 in the cam bar receiving slots 66 of the blade mounting blocks 20. The resulting camming action which is produced forces the blade mounting blocks 20 to pivot about the fixed pivot pins `44 in the housing slots 22 of the hub 12 in such a direction as to compress the biasing springs 50.

The camming action moves the propeller blade shafts 18 along Iwith the mounting blocks 20 in planes parallel to the longitudinal axis of the axis of rotation o-f the propeller. The upper limit of travel of the mounting block 20 and the blade shafts 18 rotatably journalled therein is such that the bifurcated blade actuating levers 3'6 on the said blade shafts in cooperation with the fixed pin 38 in the hub section `1.2. causes the blade shafts 18 to rotate the blades `fdl yto a position of minimum forward pitch.

The locking or indexing surfaces 63 and 69 are now in abutment and prevent the spring S from biasing the propeller to a re-verse pitch position. In the present position, the upper limit of travel of the blade mounting block Ztl provided by the cooperation between the cam surfaces 62 and 68 and the indexing or locking surfaces '63 and 69 of the cam bar 60 and the blade mounting blocks 2t respectively, is -not sufficient to fully compress the biasing springs 5b between the mounting blocks Ztl and the inner end walls 24 of the block housing slots 22. Subsequent-ly, as the propeller starts to rotate at a relatively slow rpm., the blade pitch remains at a minimum and the load on the motor is also minimized. As the r.p\.m. is increased, however, the thrust exerted between the propeller itl and the water in which it is submerged via the blades 14 begins to incre-ase as a function of the number of rpm. As a result, the thrust which is exerted parallel to the axis of rotation of the propeller, by the reaction with the water or the like is directly transmitted to the blade shafts 'i3 and the mounting blocks 2t) in which they are journalled. This causes the mounting blocks Ztl and blade shafts 1% to pivot about the fixed pins d4 against the action of the springs Sti. Now, the bifurcated blade actuating levers 36 cooperate :further with the fixed pins 38 on the hub 12 to progressively rotate the blade shafts 18 and Ivary the pitch of the blades `i4 to a maximum forward pitch at the high values of r.p.m.

The reverse pitch position :of the propeller blades 14 is effected by reversing the direction of operation of the Bowden cable 73, clamp 82, shift lever Sti, stirrup 34, yoke 86 and shift rod S4 where-by the cam bar 60 is moved inward with respect to the bottom of the guide slot 64 in the hub 12.

This actuation of the cam bar 60 permits the indexing surfaces 63 thereon to disengage the `cooperating indexing surfaces 69 in the cam bar receiving slots 66 of the blade mounting blocks 20 which allows the spring 60 to force the blade mounting blocks 20 to the position shown in solid lines in FIGS. 2 and 4. In this position, the earn surfaces 62 tand 63 on the cam lbar 6) and within the cam bar receiving slot 66 of the mounting block 20, respectively, are completely out of engagement and the front edges of the mounting blocks 2t) adjacent the annular bearing collars 28 lon the blade shafts i3 are resting on the bottom surfaces of the block housing slots 22.

Since the direction of thrust is now reversed due to the extreme reverse pitch which has been imparted to the blades, the effective force of the thrust acts to maintain the mounting blocks 2G and, hence, the blades 14 via the blade shafts 18, the bifurcated lever arm 36 thereon fand the xed pins 38 on the hub section i2', in the extreme reverse pitch position. The change back to the automatic, progressively variable, forward pitch position of the propel-ler blades 14 is again4 accomplished as outlined above by reversing the pull on the Bowden cable '78 and subsequently causing the camming and locking action between the cam bar 66 and the blade mounting blocks Z0.

As can be seen from the foregoing description in conjunction with the drawings, this invention provides a reliable, positive `pitch reversing means for boat propellers and the like which completely eliminates the necessity for a shiftable transmission in a motor with which it is used. 'In addition, the forward pitch position of the propeller Kof this invention provides ya fully automatic pitch varying means which is directly proportional to propeller thrust as a function of the number of rpm. at which it is driven. This readily permits the highly `desirable feature of direct drive with a low rpm. idle since the pitch of the blades 6 is at ia minimum under these conditions and does not cause engine overload or the like.

It is to be understood that the embodiments described in the foregoing specification land drawings 'are for the purpose of exarnple only and are not intended to limit the scope of the appended claims.

-l claim:

1. A variable pitch propeller comprising, a plurality of propeller blades, a hub, individual mounting means tadjustably positionable in said hub for adjustably retaining each of said blades therein, a blade shaft extending longitudinally of each blade and rotatably journalled in said mounting means, actuating means on said blade shaft, means on said hub cooperating with said actuating means for rotating said blade shaft in response to movement of said mounting means, indexing means mounted in said hub in operative driving relationship with said mounting means, whereby upon iactuation of said indexing means and the resulting movement of said mounting means to an extreme position in one `direction said blades assume a reverse pitch and upon actuation of said indexing means to an extreme position in the other direction said blades assume a minimum forward pitch by the rotation of said blade shafts caused by the cooperation of said lactuating means thereon with the said means on said lhub for rotating said blade shaft in response to movement of said mounting means, fwd biasing means between said mounting means and said hub 'acting to force said mounting means and said blades towards a position corresponding to said minimum [forward pitch of said blades, said mounting means and said blade shafts, in the position corresponding to forward -blade pitch, being adjustably movable against the action of said biasing means by the thrust delivered by said propeller t-o automatically and progressively vary the forward pitch of said blades from the minimum pitch to the maximum pitch as said thrust iS increased.

2. Ln a propeller including a recessed hub section and a plurality of propeller blades, blade mounting means for changing the pitch of `said blades comprising, a blade sha'ft extending longitudinally of each of said blades, mounting blocks for said blade shafts pivotally mounted within said recessed liub section, said blade shafts being mounted for pivotal movement with said mounting blocks and journalled for rotation therein, -an actuating lever on each of said blade Ishafts adjacent the outer periphery of said ihub section, `and stop means in said hub in juxtaposition with said actuating lever for actuating same in response to the pivotal movement of said mounting blocks and said blade shafts whereby said blade shafts are rotated to vary the pitch of said blades.

3. In -a propeller, including a recessed hub section and 'a plurality of propeller blades, means for :automatically varying the pitch of said blades in proportion to the thrust delivered by said propeller along the axis of rotation thereof, comprising, la blade shaft extending lonigtudinally of each of said blades, mounting blocks for said blade shafts pivotally mounted within said recessed hub section, said blade shafts being mounted 'for pivotal move- 'ment with said mounting blocks and journalled for rotation therein, an actuating lever on each of said blade shafts adjacent the outer periphery of said hub sections, stop means in said hub in juxtaposition with said actuating lever for actuating same to rotate said blade shafts in response to the pivotal movement of said shafts and said mounting blocks, biasing means between said mounting blocks and said hub acting to force said mounting blocks land said blade shafts to one extreme pivoted position thereof corresponding to an extreme reverse pitch of said blades, and indexing means in said hub in operative engagement with said mounting blocks for positioning said blocks in ian intermediate pivoted position thereof corresponding to a minimum forward pitch of said blades, said mounting blocks and said blade shafts being thereafter adjustably movable against the action of said biasing by the thrust delivered by the said propeller to automatically and progressively vary the `forward pitch of said blades from the minimum pitch to the maximum pitch las said thrust is increased.

4.V The invention as delined in claim 3 wherein said indexing means comprises `a reciprocating cam means including opposite alternate cam surfaces and adjacent indexing sunfaces and cooperating recessed cam and indexing surfaces in each of said mounting blocks defining a wall of a recess therein for receiving a portion of said recipnocating cam means.

5. The invention as dened in claim 3 wherein said indexing means comprises a reciprocating shift rod slidlably disposed internally of said hub along the axis of rotation thereof, rst cam and indexing means mounted on said shift rod, and cooperating clam and indexing means integr-al With said mounting blocks, whereby movement of said shift rod in one direction disengages said first cam and indexing means ffrom said cooperating cam and indexing means which permits said biasing means to force said mounting block to a position corresponding to maximum reverse pitch of said blades and movement of said shift rod in the other direction engages iirst said cam surfaces land second said indexing surfaces to move said mounting .blocks to iand lock them in a position correspending to the minimum forward pitch for said blades.

6. A variable pitch propeller comprising, a pluraiity of propeller blades, a hub, means in said hub for adjustably retaining each of said blades therein, control means acting on said means for shifting said blades to and from a position of-rnaximum reverse pitch from and to, respectively, a position lof minimum forward pitch and biasing means acting between said hub and said means in said: hub whereby said blades are biased toward minimum forward pitch in the forward pitch position thereof, said blades being automatically adjustable against the action of said biasing means, in the forward pitch direction to increase their pitch -as a direct function of propeller thrust.

7. A variable pitch propeller comprising, a plurality of propeller blades, a hub, individual mounting means adjustably positionable in said hub for adjustably retaining each of said blades therein, la blade shaft extending longitudinally of each lblade `md rotatably journalled in said mounting means, actuating means on said blade shaft, means on said hub cooperating with said actuating means for rotating said blade shaft in resp-onse to movement of said mounting means, indexing means mounted in said hub in operative driving relationship with said mounting means, whereby upon actuation of said indexing means and the resulting movement off said mounting means to an extreme position in one direction said blades assume a reverse pitch and upon actuation of said indexing means to an extreme position in the other direction said blades assume a forward pitch by the rotation of said blade shafts caused by the cooperation of said actuating means thereon with the said means on said hub for rotating said blade shaft in response to movement of said mounting means; and wherein said mounting means for said blades are pivotally mounted in said hub rand said blade shafts are so mounted therein that any linear movement of theV said mounting means and blade shafts is in a plane parallel the axis of notati-on of said hub.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A VARIABLE PITCH PROPELLER COMPRISING, A PLURALITY OF PROPELLER BLADES, A HUB, INDIVIDUAL MOUNTING MEANS ADJUSTABLY POSITIONABLE IN SAID HUB FOR ADJUSTABLY RETAINING EACH OF SAID BLADES THEREIN, A BLADE SHAFT EXTENDING LONGITUDINALLY OF EACH BLADE AND ROTATABLY JOURNALLED IN SAID MOUNTING MEANS, ACTUATING MEANS ON SAID BLADE SHAFT, MEANS ON SAID HUB COOPERATING WITH SAID ACTUATING MEANS FOR ROTATING SAID BLADE SHAFT IN RESPONSE TO MOVEMENT OF SAID MOUNTING MEANS, INDEXING MEANS MOUNTED IN SAID HUB IN OPERATE DRIVING RELATIONSHIP WITH SAID MOUNTING MEANS, WHEREBY UPON ACTUATION OF SAID INDEXING MEANS AND THE RESULTING MOVEMENT OF SAID MOUNTING MEANS TO AN EXTREME POSITION IN ONE DIRECTION SAID BLADES ASSUME A REVERSE PITCH AND UPON ACTUATION OF SAID INDEXING MEANS TO AN EXTERME POSITION IN THE OTHER DIRECTION AND BLADES ASSUME A MINIMUM FORWARD PITCH BY THE ROTATION OF SAID BLADE SHAFTS CAUSED BY THE COOPERATION OF SAID ACTUATING MEANS THEREON WITH THE SAID MEANS ON SAID HUB FOR ROTATING SAID BLADE SHAFT IN RESPONSE TO MOVEMENT OF SAID MOUNTING MEANS, AND BIASING MEANS BETWEEN SAID MOUNTING MEANS AND SAID HUB ACTING TO FORCE SAID MOUNTING MEANS AND SAID BLADES TOWARDS A POSITION CORRESPONDING TO SAID MINIMUM FORWARD PITCH OF SAID BLADES, SAID MOUNTING MEANS AND SAID BLADE SHAFTS, IN THE POSITION CORRESPONDING TO FORWARD BLADE PITCH, BEING ADJUSTABLY MOVABLE AGAINST THE ACTION OF SAID BIASING MEANS BY THE THRUST DELIVERED BY SAID PROPELLER TO AUTOMATICALLY AND PROGRESSIVELY VARY THE FORWARD PITCH OF SAID BLADES FROM THE MINIMUM PITCH TO THE MAXIMUM PITCH AS SAID THRUST IS INCREASED. 